This invention concerns roller cams which are widely used in die presses to carry out such functions as piercing holes into a workpiece which is engaged in the press by forming dies. Roller cams utilize a roller engaged by a driver which is fixed to a press platen, which roller is mounted to a slide so as to be advanced by a ramp surface as the driver is advanced by the platen motion. Sliding cams are not operated at angles other than horizontal due to friction, and are more bulky and costly than roller cams.
A spring is used to return the slide in roller cams. However, if stripping is necessary as when piercing the workpiece with punch tooling, the tool must be withdrawn by the force of the spring while the workpiece is held. Mechanical springs normally are not strong enough to do this, necessitating the use of more powerful devices such as nitrogen gas springs.
Also, if the spring fails, the roller cam will malfunction as there is no force generated in that event available to return the slide.
It is an object of the present invention to provide a roller cam which provides a failsafe return of the slide even when part stripping is necessary.